If the number of workers is multiplied by 12/8, the number of hours worked per day is multiplied by 8/6, and the number of days worked by each worker is multiplied by 12/27, it seems reasonable to calculate that 12 workers who work 8 hours a day for 12 days can dig 6 Ã— 12/8 Ã— 8/6 Ã— 12/27 holes of 18 meter depth. That 16/3 holes.
If the holes need to be 24 meters deep, instead of 18 meters deep, let's assume that it's necessary to multiply by 18/24. As 16/3 Ã— 18/24 = 4, the final answer is 4.